MongoDB Shell 学习（二）

本节主要讲述怎么去学习好shell
1.利用shell自带的帮助命令
> help
        db.help()                    help on db methods
        db.mycoll.help()             help on collection methods
        rs.help()                    help on replica set methods
        help connect                 connecting to a db help
        help admin                   administrative help
        help misc                    misc things to know
        help mr                      mapreduce help

        show dbs                     show database names
        show collections             show collections in current database
        show users                   show users in current database
        show profile                 show most recent system.profile entries wit
h time >= 1ms
        use <db_name>                set current database
        db.foo.find()                list objects in collection foo
        db.foo.find( { a : 1 } )     list objects in foo where a == 1
        it                           result of the last line evaluated; use to f
urther iterate
        DBQuery.shellBatchSize = x   set default number of items to display on s
hell
        exit                         quit the mongo shell
2.使用db.help()查看数据库级别命令的帮助
> db.help();
DB methods:
        db.addUser(username, password[, readOnly=false])
        db.auth(username, password)
        db.cloneDatabase(fromhost)
        db.commandHelp(name) returns the help for the command
        db.copyDatabase(fromdb, todb, fromhost)
        db.createCollection(name, { size : ..., capped : ..., max : ... } )
        db.currentOp() displays the current operation in the db
        db.dropDatabase()
        db.eval(func, args) run code server-side
        db.getCollection(cname) same as db['cname'] or db.cname
        db.getCollectionNames()
        db.getLastError() - just returns the err msg string
        db.getLastErrorObj() - return full status object
        db.getMongo() get the server connection object
        db.getMongo().setSlaveOk() allow this connection to read from the nonma
ter member of a replica pair
        db.getName()
        db.getPrevError()
        db.getProfilingLevel() - deprecated
        db.getProfilingStatus() - returns if profiling is on and slow threshold
2.使用db.foo.help()查看集合相关帮助
> db.blog.help()
DBCollection help
        db.blog.find().help() - show DBCursor help
        db.blog.count()
        db.blog.dataSize()
        db.blog.distinct( key ) - eg. db.blog.distinct( 'x' )
        db.blog.drop() drop the collection
        db.blog.dropIndex(name)
        db.blog.dropIndexes()
        db.blog.ensureIndex(keypattern[,options]) - options is an object with th
ese possible fields: name, unique, dropDups
        db.blog.reIndex()
        db.blog.find([query],[fields]) - query is an optional query filter. fiel
ds is optional set of fields to return.
                                                      e.g. db.blog.find( {x:77}
, {name:1, x:1} )
        db.blog.find(...).count()
        db.blog.find(...).limit(n)
        db.blog.find(...).skip(n)
        db.blog.find(...).sort(...)
        db.blog.findOne([query])
        db.blog.findAndModify( { update : ... , remove : bool [, query: {}, sort
: {}, 'new': false] } )
        db.blog.getDB() get DB object associated with collection
4.查看函数的JavaScript源码
> db.blog.find
function (query, fields, limit, skip) {
    return new DBQuery(this._mongo, this._db, this, this._fullName, this._massag
eObject(query), fields, limit, skip);
}